System for controlling an earthworking implement

ABSTRACT

A method for controlling an earthworking implement of an earthworking machine is disclosed. The method includes determining a first depth of cut of the earthworking implement at least partially based on a power capability of the earthworking implement. The method also includes determining a second depth of cut of the earthworking implement at least partially based on a desired grade of a work site. The method further includes moving the earthworking implement in response to at least one of the first depth of cut and the second depth of cut.

TECHNICAL FIELD

The present disclosure relates generally to a method and apparatus for controlling an earthworking implement, and more particularly, to a method and apparatus for controlling an earthworking implement with respect to a working depth of cut.

BACKGROUND

Earthworking machines such as, for example, dozers, loaders, excavators, motor graders, and other types of earth moving machines, are often used to remove material from a work site to achieve a desired work site grade. Specifically, it may be desired to remove a layer of a first material to expose a second material located beneath the first layer. For example, it may be desired to remove a layer of dirt and/or rock to expose a valuable layer of coal or other ore. Additionally, it may be desired to remove a layer of material to achieve a desired grade to prepare a work site for further construction. For example, it may be desired to remove a layer of dirt and/or rock to establish a desired grade for a parking lot or road.

Methods have been employed to control earthworking machines and, in particular, earthworking implements during the material removal process. For example, U.S. Pat. No. 5,819,190 (“the '190 patent”) issued to Nakagami et al. discloses a control system which monitors variables of an earthworking implement and of an earthworking machine and responsively controls the earthworking implement relative to material to be removed. Specifically, the system of the '190 patent determines the operational cutting edge position of an earthworking implement with respect to the ground and controls the earthworking implement to be raised or lowered to be kept coincident with a preset target cutting edge position.

Although the system of the '190 patent may automatically control the depth of cut of an earthworking implement, the earthworking implement may be undesirably controlled because the system of the '190 patent may not account for depth of cut differences between a desired contour of the work site and the capability of the earthworking machine to remove material from the work site. Specifically, the earthworking implement of the '190 patent may be controlled to remove material desired to remain in the work site, thus wasting valuable material and/or requiring material to be replaced to achieve a desired grade. Additionally, the earthworking implement of the '190 patent may be controlled to remove less material than desired from the work site, thus wasting earthworking implement productivity.

The disclosed method and apparatus for controlling an earthworking implement is directed to overcoming one or more of the problems set forth above.

SUMMARY OF THE INVENTION

In one aspect, the present disclosure is directed to a method for controlling an earthworking implement of an earthworking machine. The method includes determining a first depth of cut of the earthworking implement at least partially based on a power capability of the earthworking implement. The method also includes determining a second depth of cut of the earthworking implement at least partially based on a desired grade of a work site. The method further includes moving the earthworking implement in response to at least one of the first depth of cut and the second depth of cut.

In another aspect, the present disclosure is directed to a method of moving an earthworking implement of an earthworking machine which includes moving the earthworking implement toward a first depth of cut. The first depth of cut being at least partially based on a desired grade. The method also includes automatically moving the earthworking implement toward a second depth of cut. The second depth of cut being different than the first depth of cut and the second depth of cut being at least partially based on a power capability of the earthworking implement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial illustration of a exemplary disclosed earthworking machine;

FIG. 2 is a schematic illustration of a control system of the disclosed earthworking machine of FIG. 1; and

FIG. 3 is an exemplary block diagram of a method of the disclosed control system of FIG. 2.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary earthworking machine 12. Earthworking machine 12 may be a mobile machine that performs some type of operation associated with an industry such as mining, construction, farming, or other industry known in the art. For example, earthworking machine 12 may be a dozer, a loader, a backhoe, an excavator, a motor grader, or any other earthworking machine known in the art. Earthworking machine 12 may be configured to traverse a work site 10 to remove material 100 from and/or add material 100 to locations within work site 10. Earthworking machine 12 may include a frame 14, an earthworking implement 16, and a control system 18.

Frame 14 may include any structural unit that supports movement of earthworking machine 12. Frame 14 may be, for example, a stationary base frame connecting a power source (not shown) to a traction device 24, a movable frame member of a linkage system, or any other type of frame known in the art. It is contemplated that traction device 24 may include tracks, wheels, and/or other traction devices known in the art.

Earthworking implement 16 may include a device used in the performance of material handling. For example, earthworking implement 16 may include a blade, a scraper, a bucket, a shovel, and/or other types of earthworking implements known in the art. Earthworking implement 16 may be coupled to frame 14 via a hydraulic cylinder 20 and a linkage system 22 and may be selectively movable relative to frame 14 by hydraulic cylinder 20. Additionally, earthworking implement 16 may be moved relative to a surface 102 of material 100 to remove material 100 from work site 10. Earthworking implement 16 may be configured to pivot, rotate, slide, swing, or otherwise move relative to frame 14 in any manner known in the art. It is contemplated that earthworking implement 16 may include multiple earthworking implements.

Referring to FIG. 2, control system 18 may be configured to control the operation of earthworking machine 12 and, in particular, configured to control earthworking implement 16. Control system 18 may include a command controller 400, a productive controller 402, and a contour controller 404, and may be configured to interact with hydraulic cylinder 20 to control the extension and/or retraction thereof to affect movement of earthworking implement 16. Control system 18 may also be configured to interact with auxiliary devices 50 such as, for example, a power source, a steering apparatus, drive train apparatus, and/or other devices used to operate earthworking machine 12 and/or components thereof to selectively and/or dynamically affect movement thereof over work site 10. It is contemplated that control system 18 may additionally include other components, such as, for example, operator interfaces, visual displays, warning indicators, sensors, and/or other components known in the art to display, affect, and/or control the operation of earthworking machine 12 and/or components thereof. It is also contemplated that control system 18 may include command controller 400, productive controller 402, and contour controller 404 embodied as a single controller, two controllers, and/or any number of controllers, as desired.

Productive controller 402 may be configured to determine a productive depth of cut of earthworking implement 16 relative to surface 102 to maximize the productive removal of material 100 from work site 10. The productive depth of cut may be based in part on the power capability of earthworking implement 16, which may be based in part on the ability of earthworking implement 16 to productively remove material 100 from work site 10. Productive controller may be further configured to output a command signal D_(P), indicative of the determined productive depth of cut, to command controller 400 to affect the movement of earthworking implement 16 in response to the determined productive depth of cut. For example, if productive controller 402 determines that earthworking implement 16 is operating at a depth of cut shallower than an optimal productivity, e.g., earthworking implement 16 may be unproductively removing too small an amount of material 100, productive controller 402 may be configured to output command signal D_(P) to command controller 400 which would lower earthworking implement 16 deeper into material 100. Similarly, if productive controller 402 determines that earthworking implement 16 is operating at a depth of cut deeper than an optimal predetermined productivity, e.g., earthworking implement 16 may be unproductively removing too great an amount of material 100, productive controller 402 may be configured to output command signal D_(P) to command controller 400 which would raise earthworking implement 16 higher within material 100. As such, productive controller 402 may output, to command controller 400, command signal D_(P) adapted to control the depth of cut of earthworking implement 16 within material 100 to achieve a productive removal thereof. It is contemplated that productive controller 402 may dynamically output command signal D_(P) to command controller 400 in response to varying work site conditions and/or other conditions that may affect command signal D_(P), such as, for example, operational capabilities of earthworking machine 12 and/or material properties of material 100.

For example, productive controller 402 may determine the productive depth of cut and output command signal D_(P) through a predetermined algorithm as a function of signals received from a ground speed sensor (not shown), a slope detector (not shown), a slip detector (not shown), and/or a tilt sensor (not shown). The power of earthworking implement 16 may be determined and/or based in part on the sensed ground speed of earthworking machine 12, the detected slope of work site 10, the detected slip of traction device 24, the sensed tilt of earthworking implement 16, and/or the relationships thereof with the amount of material 100 being removed by earthworking implement 16. Productive controller 402 may be configured to determine the productive depth of cut based in part on the power of earthworking implement 16 determined by the predetermined algorithm analyzing the sensed data and/or comparing such data with look-up tables, databases, and/or other known mathematical manipulations. Additionally, productive controller 402 may be configured to determine the actual depth of cut of earthworking implement 16 in part based on the position of earthworking implement 16 relative to earthworking machine 12 and/or surface 102 and compare the determined productive depth of cut and the actual depth of cut to output command signal D_(P) to affect movement of earthworking implement 16 toward the productive depth of cut. It is contemplated that productive controller 402, through the predetermined algorithm, may also determine command signal D_(P) based in part on error feedback terms and mathematical constants as is known in the art. Productive controller 402 may embody any known or conventional apparatus and method configured to maximize the productive removal of material from a work site. It is further contemplated that productive controller 402 may include any controller, method, and/or algorithm configured to determine a depth of cut based on the power capability of an earthworking implement by analyzing, sensing, and/or monitoring known operational parameters of the earthworking implement, an earthworking machine, and/or work site properties.

Contour controller 404 may be configured to determine a contour depth of cut of earthworking implement 16 relative to surface 102 to remove material 100 from worksite 10 to achieve a desired grade. Contour controller 404 may be further configured to output a command signal D_(C), indicative of the determined contour depth of cut, to command controller 400 to affect the position of earthworking implement 16 in response to the determined contour position. For example, if contour controller 404 determines that earthworking implement 16 is operating at a depth of cut above a predetermined desired grade, i.e., earthworking implement 16 is not removing material that is desired to be removed, contour controller 404 may be configured to output command signal D_(C) which would command controller 400 to lower earthworking implement 16 deeper into material 100. Similarly, if contour controller 404 determines that earthworking implement 16 is operating at a depth of cut below a predetermined desired level, i.e., earthworking implement 16 is removing material 100 that is desired to remain, contour controller 404 may be configured to output command signal D_(C) which would command controller 400 to raise earthworking implement 16 higher within material 100. As such, contour controller 404 may output, to command controller 400, command signal D_(C) adapted to control the depth of cut of earthworking implement 16 within material 100 to achieve a desired grade. It is contemplated that contour controller 404 may additionally include command outputs to control and/or operate warning signals, alarms, visual displays, and/or other informational components that may be activated to indicate an operating status of contour controller 404 and, in particular, earthworking implement 16 and earthworking machine 12. It is contemplated that contour controller 404 may dynamically output command signal D_(C) to command controller 400 in response to varying work site conditions and/or other conditions that may affect command signal D_(C), such as, for example, varying depth of desired contour and/or varying contour of surface 102.

For example, contour controller 404 may determine the contour depth of cut through a predetermined algorithm based in part on work site geographies and may include a desired work site geography model and an actual work site geography model. Contour controller may be configured to receive an initial work site geography determined, for example, by manual site survey, automated site survey systems utilizing stereo photography and data processors, and/or geological core sampling methods. The initial work site geography model may be stored within a data storage device (not shown) and configured to be accessible by a global positioning system (“GPS”) via the algorithm. As earthworking machine 12 traverses work site 10, the GPS may be further configured to monitor position coordinates of earthworking machine 12 relative to work site 10 and communicate data to the algorithm, which in turn may determine the actual work site geography as changes are made thereto by earthworking implement 16. Contour controller 404 may also be configured to determine the position of earthworking implement 16 relative to earthworking machine 12. Contour controller 404 may be further configured to output command signal D_(C) based on the difference between the actual and desired work site geography models to control earthworking implement 16 and/or earthworking machine 12 to remove material 100 and bring the actual work site into conformity with the desired work site geography model. It is further contemplated that contour controller 404 may include any controller, method, and/or algorithm configured to determine a depth of cut of an earthworking implement based in part on a desired grade of a work site by analyzing, sensing, and/or monitoring known operational parameters and/or locations of the earthworking implement, an earthworking machine, and/or work site properties.

Command controller 400 may be configured to monitor and regulate command signals D_(P) and D_(C) outputted from productive controller 402 and contour controller 404, respectively, to thereby control movement of earthworking implement 16. Command controller 400 may receive command signals D_(P) and D_(C) and may determine which of command signals D_(P) or D_(C) would control earthworking implement to operate at a higher depth of cut within material 100. Command controller 400 may further be configured to output a command signal D_(I) indicative of one of command signals D_(P) and D_(C) determined to control earthworking implement 16 to a higher depth of cut. Command controller 400 may further be configured to output command signal D_(I) to affect movement of hydraulic cylinder 20, via a hydraulic circuit (not shown), to control earthworking implement 16 to a working depth of cut. Additionally, command controller 400 may be configured to override the other one of command signals D_(P) and D_(C) not determined to control earthworking implement 16 to a higher depth of cut. It is contemplated that command controller may allow the one of command signals determined to control earthworking implement 16 to a higher depth of cut to directly control hydraulic cylinder 20 to the working depth of cut. It is also contemplated that command controller 400 may alternatively control other components of earthworking machine 12 to affect the movement of earthworking implement 16 to the working depth of cut, such as, for example, hydraulic valve actuators, direct electronic actuators, mechanically geared actuators, and/or other components known in the art. It is also contemplated that command controller 400, productive controller 402, and contour controller 404 may be integrated into a common controller. It is further contemplated that command controller 400 may additionally affect and/or control operation and movement of earthworking machine 12 over work site 10.

FIG. 3 illustrates an exemplary method 500 of command controller 400 to control movement of earthworking implement 16. Method 500 may include a comparing command signal D_(P) and command signal D_(C), step 502, outputting a command signal D_(I) indicative of command signal D_(C), step 504, and outputting a command signal D_(I) indicative of command signal D_(P). Specifically, method 500 may compare command signals D_(P) and D_(C) in step 502 and determine if command signal Dc corresponds to a higher depth of cut than command signal D_(P). If command signal D_(C) corresponds to a higher depth of cut, method 500 may progress to step 504 wherein command controller may output command signal D_(I) indicative of command signal D_(C). If command signal D_(C) does not correspond to a higher depth of cut, method 500 may progress to step 506 wherein command controller may output command signal D_(I) indicative of command signal D_(P).

Step 502 may compare command signals D_(P) and D_(C) and determine if command signal D_(C) would affect movement of earthworking implement 16 to a higher depth of cut than command signal D_(P). The comparison of command signals D_(P) and D_(C) and the determination of whether command signal D_(C) would control earthworking implement 16 to a higher depth of cut than would command signal D_(P) may be determined by an algorithm and may be based in part on look-up tables, calculations, and/or other mathematically suitable methods known in the art to compare signals.

Step 504 may include command controller 400 outputting command signal D_(I) configured to affect control of earthworking implement 16 to a depth of cut indicative of command signal D_(C). Specifically, command signal D_(I) may be in part based on command signal D_(C) and may control the movement of earthworking implement 16 via hydraulic cylinder 20. Additionally, command controller 400 may prohibit command signal D_(P) from affecting movement of earthworking implement 16. Specifically, command controller 400 may selectively suspend productive controller 402 from outputting command signal D_(P).

For example, command controller 400 may selectively suspend command signal D_(P) from affecting movement of earthworking implement 16. Command controller 400 may selectively suspend command signal D_(P) by an integrated circuit logic, an algorithm and/or other control means known in the art. It is contemplated that command controller 400 may also selectively suspend calculation of any error feedback terms. Specifically, command controller 400 may override the calculation of the error feedback term by fixing the term to zero by an integrated circuit logic, an algorithm and/or other control means known in the art. Selectively overriding the calculation of any error feedback terms may eliminate productive controller 402 from outputting command signal D_(P) which would affect a large actuation of earthworking implement 16 when command controller 400 outputs command signal D_(I) indicative of command signal D_(P) subsequent to outputting command signal D_(I) indicative of command signal D_(C).

Step 506 may include command controller 400 outputting command signal D_(I) to affect control of earthworking implement 16 to a depth of cut indicative of command signal D_(P) when command signal D_(C) is not higher than command signal D_(P). Specifically, command signal D_(I) may be based in part on command signal D_(P) and may control the movement of earthworking implement 16 via hydraulic cylinder 20. Additionally, command controller 400 may prohibit command signal D_(C) from affecting movement of earthworking implement 16. Specifically, command controller 400 may selectively suspend contour controller 404 from outputting command signal Dc and other command signals which would control earthworking machine 12 and/or earthworking implement 16, and also control additional instructional and/or warning signals indicative of the operating status of contour controller 404 and earthworking machine 12.

For example, command controller 400 may selectively suspend command signal D_(C). Command controller 400 may selectively suspend command signal D_(C) by an integrated circuit logic, an algorithm and/or other control means known in the art. It is contemplated that command controller 400 may also selectively suspend additional instructional and/or warning signals indicative of the operating status of contour controller 404 and earthworking machine 12 by an integrated circuit logic, an algorithm and/or other control means known in the art.

Method 500 may additionally be configured to return to control 502 after steps 504, 506. Specifically, subsequent to command controller outputting command signal D_(I) indicative of command signal D_(C) or D_(P), command controller may monitor and again compare command signals D_(C) and D_(P). After a subsequent determination in step 502 regarding command signals D_(C) and D_(P), method 500 may progress to step 504 or step 506 and method 500 may be repeated as necessary or desired by an operator to remove material 100 from work site 10. As such, method 500 may continuously monitor and compare command signals D_(C) and D_(P) and command controller 400 may dynamically output command signal D_(I) indicative of the one of command signals D_(C) and D_(P) that would control earthworking implement to a higher depth of cut. It is contemplated that method 500 may further include additional steps such as, for example, an initialization step (not shown), an end step (not shown), a suspend/pause step (not shown), or other control features known in the art.

INDUSTRIAL APPLICABILITY

The disclosed method and apparatus of controlling an earthworking implement may be applicable to any earthworking machine that removes material from a work site. The disclosed method and apparatus may provide productive material removal while bringing actual work site geography into desired work site geography. The operation of the method and apparatus of controlling earthworking implement 16 is explained below.

Earthworking machine 12 may be used to remove material 100 from work site 10 to achieve a desired grade. Specifically, earthworking machine 12 may traverse work site 10 to remove material 100 to expose a layer of desired material and/or provide a desired contour. As earthworking machine 12 traverses work site 10, earthworking implement 16 may be raised and/or lowered relative to surface 102 of material 100 to affect the removal of material 100 from work site 10. As earthworking implement 16 affects removal of material 100, control system 18 may monitor and control the position of earthworking machine 12 relative to work site 10 and the position of earthworking implement 16 relative to earthworking machine 12 to productively remove material 100 while achieving a desired grade.

As earthworking machine traverses work site 10, productive controller 402 may output control signal D_(P) to command controller 400 that would control earthworking implement 16 to be moved relative to surface 102. Specifically, productive controller 402 may determine that earthworking implement, and earthworking machine 12, may be capable of removing more material 100 than that currently being removed and/or may be currently be removing too much material 100. Substantially simultaneously, contour controller 404 may output command signal D_(C) to command controller 400 that would control earthworking implement 16 to be moved relative to surface 102. Specifically, contour controller 404 may determine that surface 102 of material 100 is not the desired grade and thus that material 100 needs to be removed and/or that surface 102 is the desired grade and that no material 100 needs to be removed.

Command controller 400 may compare (referring to FIG. 3) command signals D_(P) and D_(C) to determine which of command signals D_(P) and D_(C) is configured to control earthworking implement 16 to a higher depth of cut below surface 102. Command controller 400 may then output command signal D_(I), indicative of the one of productive controller 402 and contour controller 404 that would control earthworking implement 16 to a higher depth of cut to thereby control earthworking implement 16. For example, if command controller 400 determines that command signal D_(C) would control earthworking implement 16 to a higher depth of cut (i.e., productive controller 402 would control earthworking implement below the desired grade), command controller 400 may output command signal D_(I) indicative of command signal D_(C) to control earthworking implement 16. Similarly, if command controller 400 determines that command signal D_(P) would control earthworking implement 16 to a higher depth of cut (i.e., contour controller 404 would control earthworking implement 16 to a depth at which earthworking implement 16 may no longer productively remove material 100), command controller 400 may output command signal D_(I) indicative of command signal D_(P) to control earthworking implement 16. It is contemplated that command controller 400 may, alternatively, allow the one of command signals D_(P) and D_(C) that would control earthworking implement 16 to a higher depth of cut to directly control earthworking implement 16.

The following operation of control system 18, and in particular, command controller 400 is illustrated with reference to earthworking machine 12 during several passes across work site 10 from a unmodified work site toward a desired grade. It is noted that the explanation below is for clarification purposes only, and the method and apparatus may be applicable for any earthworking machine at any status of material removal from work site 10.

For example, as earthworking machine 12 makes a first pass across work site 10, earthworking implement 16 may be positioned above surface 102 and may not remove material 100. It is likely, however, that surface 102 may not be at the desired grade and both productive controller 402 and contour controller 404 may determine and output respective command signals D_(P) and D_(C) that would lower earthworking implement 16 below surface 102. Specifically, productive controller 402 may output a command signal D_(P) to command controller 400 that would lower earthworking implement 16 to a productive depth of cut to productively remove material 100. Similarly, contour controller 404 may substantially simultaneously output command signal D_(C) to command controller 400 that would lower earthworking implement 16 toward a contour depth of cut to achieve a desired grade. It is noted that command signals D_(P) and D_(C) may each affect a lowering of earthworking implement 16 toward the desired grade of work site 10. Command controller 400 may monitor and determine which of command signals D_(P) and D_(C) would control earthworking implement 16 to a higher depth of cut (see FIG. 3, step 502). Because surface 102 may not be at the desired grade, command controller 400 may move earthworking implement 16 lower into material 100 below surface 102 in response to one of command signals D_(P) or D_(C). It is contemplated that earthworking implement 16 may gradually be lowered into material 100 below surface 102 to begin removing material 100 due to movement of earthworking machine 12 relative to work site 10 and time necessary to move earthworking implement 16 from an preexisting depth of cut to subsequent depth of cut.

Assuming that a relatively small amount of material 100 is desired to be removed from work site 10, command signal D_(C) may control earthworking implement 16 to a higher depth of cut than would command signal D_(P). Specifically, command controller 400 may determine that command signal D_(C) would control earthworking implement 16 to a higher depth of cut than would command signal D_(P) (see FIG. 3, step 502) and may output command signal D_(I) to control earthworking implement 16 to a depth of cut indicative of command signal D_(C) (see FIG. 3, step 504). For example, earthworking machine 12 may be capable of moving a large amount of material 100 but only a relatively small amount of material needs to be removed to achieve the desired grade. As such, productive controller 402 may output command signal D_(P) that would, if allowed to control earthworking implement 16, lower earthworking implement 16 below the desired grade, which may be undesirable.

As earthworking machine 12 continues the first pass across work site 10 with earthworking implement 16 controlled below surface 102 of material 100, the amount of material 100 removed by earthworking implement 16 may increase. Specifically, newly removed material 100 may combine with previously removed material 100 and may build up in front of earthworking implement 16. As the amount of removed material 100 increases, earthworking implement 16 may no longer be able to productively remove material 100 at the contour depth of cut and productive controller 402 may output command signal D_(P) that would control earthworking implement 16 at a higher depth of cut than would command signal D_(C).

Command controller 400 may continually monitor command signals D_(C) and D_(P), and may determine that command D_(P) would control earthworking implement 16 to a higher depth of cut than would command signal D_(C) (see FIG. 3, step 502) and may output command signal D_(I) to control earthworking implement 16 to a depth of cut indicative of command signal D_(P) (see FIG. 3, step 506). For example, earthworking implement 16 may no longer be capable of productively removing material 100 at the desired grade as controlled by contour controller 404 because of the increasing amount of material 100 removed by earthworking implement 16. As a result, earthworking implement 16 may be raised to a higher depth of cut, i.e., earthworking implement 16 may no longer be controlled to the contour depth of cut and instead may be controlled to the productive depth of cut.

As earthworking machine 12 continues the first pass, contour controller 404 may monitor the desired work site geography and the actual work site geography and dynamically output command signal D_(C) to affect earthworking implement 16 toward a contour depth of cut. Similarly, productive controller 402 may monitor the operating conditions of earthworking machine 12 and/or earthworking implement 16 and dynamically output command signal D_(P) to affect earthworking implement 16 toward a productive depth of cut. Accordingly, command controller 400 may monitor dynamically outputted command signals D_(C) and D_(P) and may thus dynamically output command signal D_(I) to dynamically control the depth of earthworking implement 16. For example, the desired geography and/or actual geography of work site 10 may vary and command signals D_(C) and D_(P) may correspondingly vary depending upon the location of earthworking machine 12 relative to work site 10 and/or the amount of material desired to be removed. For example, the actual and/or desired grade may include variable slopes and as a result may include a dynamically changing difference between the actual grade and the desired grade resulting in contour controller 404 and productive controller 402 dynamically determining command signals D_(C) and D_(P) that would control earthworking implement 16 to respective dynamic depths of cut.

As earthworking machine 12 makes a second pass across work site 10, earthworking implement 16 may be positioned above surface 102. However, surface 102 may now be at the desired grade because during the first pass, contour controller 404 affected control of earthworking implement 16 to the desired grade. Accordingly, contour controller 404 may output command signal D_(C) that would not lower earthworking implement below surface 102 because the desired grade has been achieved. However, because earthworking implement 16 may not be removing material 100, productive controller 402 may output command signal D_(P) that would lower earthworking implement below surface 102 because earthworking implement 16 is capable of productively removing more material 100. Controller 400 may monitor command signals D_(C) and D_(P) and output command signal D_(I) indicative of command signal D_(C) to control earthworking implement 16.

As earthworking machine 12 continues the second pass, surface 102 may at some point no longer be at the desired grade. This may occur because earthworking implement 16 may have been raised during the first pass in response to command signal D_(P). Accordingly, contour controller 404 and productive controller 402 may determine and output respective command signals D_(C) and D_(P) that would lower earthworking implement 16 below surface 102. Again assuming a relatively small amount of material 100 is desired to be removed, controller 400 may output command signal D_(I) indicative of command signal D_(C) to control earthworking implement 16 toward the contour depth of cut. As earthworking machine 12 continues the second pass, and similar to the first pass, the amount of material 100 removed by earthworking implement 16 may increase and earthworking implement 16 may no longer be able to productively remove material 100 at the contour depth. Productive controller 402 may output command signal D_(P) that would control earthworking implement 16 at a higher depth of cut than would command signal D_(C) and accordingly, controller 400 may output command signal D_(I) indicative of command signal D_(P) to control earthworking implement 16.

As earthworking machine 12 makes subsequent passes across work site 10, the operation explained above may be continued as necessary to achieve the desired grade. Each subsequent pass may bring the actual work site geography closer toward the desired work site geography. It is contemplated that work machine 12 may begin subsequent passes at the point where surface 102 of material 100 is no longer at the desired grade. Specifically, earthworking machine may not need to start subsequent passes at the same origin as previous passes because the desired grade may have been achieved therein.

Because command controller 400 monitors command signals D_(P) and D_(C) and controls earthworking implement 16 in response to the one of command signals D_(P) and D_(C) that would control earthworking implement to a higher depth of cut, removal of material from work site 10 may be performed productively and to a desired grade. This monitoring may eliminate the unintended removal of material desired to remain in work site 10 and may increase the productive removal of material that is desired to be removed. The overall productivity of transforming a work site from actual geography to desired geography may be increased.

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed method and apparatus for controlling an earthworking implement. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed method and apparatus for controlling an earthworking implement. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents. 

1. A method for controlling an earthworking implement of an earthworking machine comprising: determining a first depth of cut of the earthworking implement at least partially based on a power capability of the earthworking implement; determining a second depth of cut of the earthworking implement at least partially based on a desired grade of a work site; and moving the earthworking implement in response to at least one of the first depth of cut and the second depth of cut.
 2. The method of claim 1, further including moving the earthworking implement to the determined first depth of cut when the magnitude of the determined first depth of cut is less than the magnitude of the determined second depth of cut.
 3. The method of claim 1, further including moving the earthworking implement to the determined second depth of cut when the magnitude of the determined second depth of cut is less than the magnitude of the determined first depth of cut.
 4. The method of claim 1, wherein moving the earthworking implement includes selectively moving the earthworking implement to the one of the determined first depth of cut and the determined second depth of cut having a smaller magnitude and subsequently selectively moving the earthworking implement to the other of the determined first depth of cut and the determined second depth of cut.
 5. The method of claim 1, further including producing a first depth of cut signal at least partially based on the determined first depth of cut; producing a second depth of cut signal at least partially based on the determined second depth of cut; and monitoring the first depth of cut signal and the second depth of cut signal.
 6. The method of claim 5, further including: producing a command signal at least partially based on one of the first depth of cut signal and the second depth of cut signal; and moving the earthworking implement in response to the command signal.
 7. The method of claim 5, wherein: producing the first depth of cut signal includes determining a desired productive depth of cut, determining an actual depth of cut of the earthworking implement, and determining a difference between the desired productive depth of cut and the actual depth of cut of the earthworking implement.
 8. The method of claim 7, further including: prohibiting the first depth of cut signal from affecting movement of the earthworking implement when the magnitude of the second depth of cut is less than the magnitude of the first depth of cut.
 9. The method of claim 8, wherein prohibiting the first depth of cut signal includes selectively overriding the calculated difference.
 10. The method of claim 5, wherein: producing the second depth of cut signal includes comparing an actual geographic model of a work site with a desired geographic model of the work site and determining a location of an earthworking machine and the earthworking implement with respect to the actual and desired geographic models of the work site.
 11. The method of claim 10, further including: prohibiting the second depth of cut signal from affecting movement of the earthworking implement when the magnitude of the first depth of cut is less than the magnitude of the second depth of cut.
 12. The method of claim 11, wherein prohibiting the second depth of cut signal includes selectively suspending the output of the second depth of cut signal.
 13. A method of moving an earthworking implement of an earthworking machine comprising: moving the earthworking implement toward a first depth of cut wherein the first depth of cut is at least partially based on a desired grade; and automatically moving the earthworking implement toward a second depth of cut wherein the second depth of cut is different than the first depth of cut and the second depth of cut is at least partially based on a power capability of the earthworking implement.
 14. The method of claim 13, wherein the second depth of cut is shallower than the first depth of cut, the method further including automatically moving the earthworking implement toward a third depth of cut wherein the third depth of cut is at least partially based on a desired grade.
 15. The method of claim 13, wherein the second depth of cut is shallower than the first depth of cut, the method further including automatically moving the earthworking implement toward a third depth of cut wherein the third depth of cut is shallower than the second depth of cut.
 16. The method of claim 13, wherein the second depth of cut is deeper than the first depth of cut, the method further including automatically moving the earthworking implement toward a third depth of cut wherein the third depth of cut is shallower than the second depth of cut.
 17. The method of claim 16, wherein the third depth of cut is at least partially based on the power capability of the earthworking implement.
 18. The method of claim 13, further including: controlling the earthworking implement with a control system; and dynamically outputting a command signal from the control system to automatically move the earthworking implement to one of the first and second depths of cut.
 19. The method of claim 13, further including: moving the earthworking implement to the first depth of cut wherein the first depth of cut is the desired grade; and removing a first layer of material from a work site to achieve the desired grade.
 20. An earthworking machine comprising: a frame; a traction device; a earthworking implement; a controller operably connected to the earthworking implement and configured to compare a first depth of cut signal indicative of a productive depth of cut and a second depth of cut signal indicative of a contour depth of cut and further configured to selectively move the earthworking implement to a working depth of cut in response to at least one of the first depth of cut signal and the second depth of cut signal.
 21. The earthworking machine of claim 20, wherein the controller is configured to selectively move the earthworking implement in response to the first depth of cut when the magnitude of the first depth of cut is less than the magnitude of the second depth of cut.
 22. The earthworking machine of claim 20, wherein the controller is configured to selectively move the earthworking implement in response to the second depth of cut when the magnitude of the second depth of cut is less than the magnitude of the first depth of cut.
 23. The earthworking machine of claim 20, wherein determining a productive depth of cut includes sensing one or more of the following: the speed of the earthworking machine, the slope of a work site in which the earthworking machine is located, the slip of the of the traction device, and the tilt of the earthworking implement.
 24. The earthworking machine of claim 20, wherein determining a contour depth of cut includes: comparing a desired geographic model of a work site with an actual geographic model of a work site; sensing the position of the earthworking machine relative to the desired and actual geographic models of the work site; and sensing the position of the earthworking implement relative to the earthworking machine. 